I have indeed run the kiln the old way, and tracked the temps. Running
full tilt, I know that in order to reach my target temp, the heat rate
is only around 60 degF per hour in the home stretch. This is running at
max; I'm not even maintaining a cone rate of 108DegF. So I,
respectfully, disagree with your point that "there should be no loss of
maximum performance", because when the controller turns off any of the
coils in an attemp to even the temps, then you must see that, in my
case, my heat rate must also drop below 60.

Also, regarding your statement "This is certainly not a fault of the
controller",it is certainily well taken, and, in my original post, I
did not wish to imply fault on the part of the controller. My intent
was to warn those who may have a kiln, such as mine, that may not
perform sufficiently with such a controller.

I imagine that your experience might be based on working with kilns
that have sufficient power and/or insulation qualities and that are
engineered well.

Bob Masta wrote:
Perhaps I misunderstand your problem, but the above doesn't
make sense.

The controller does indeed switch your elements on and off, but
there should be no loss of maximum performance. It's like your
kitchen oven: when the current temperature is below the setpoint,
there is maximum power to the element(s). Only when it reaches the
setpoint does it start cutting back, in order to maintain whatever
temperature you set. The difference with a digital controller is that
there is not just one simple setpoint like your oven, more like a
schedule of setpoints that it sets one after the other.

Yes, it's true that when you set a slow ramp-up, the kiln does not
heat as fast... it's just doing what you told it! This is certainly
not a fault of the controller. It's also possible to set a ramp
that is so steep that the kiln can't meet it even running flat-out.
So you do need to have some experience with your kiln to know
what is possible as far as rise rates go.

But there should never be a problem such as you describe.
You don't need any surplus power at all if you have set your
schedule to be similar to your original uncontrolled rate.
In that case, the controller will not be doing much of anything
until you hit the setpoint. Only then does it start cutting back
on the power in order to hold that temperature.

I am not an expert, so I can't give you any kind of formula to use for
determining this. However, it would seem that if you can reach your
cone reasonably by running at, say, only two-thirds of your full power
(such as running with only 4 elemnts out of 6 total), then it might
work out okay.

If not, you'll still be able to run your kiln unattended, but you will
not be able to get uniformly heated zones at the end of your fire.

Again, perhaps I have misunderstood your problem, but my
suspicion is that you have simply set an unreasonable schedule.
One thing you might consider is running the kiln the old way
and recording the temperatures every hour, then use that data
to set a controller schedule that comes close to the "natural"
kiln performance. The difference is that once you reach the
cone setting, you will now be able to hold that for as long as
you want, or to cut back to a somewhat lower setting for
crystal growth, etc.

Once you have this base ramp -up information, you can
feel free to set slower ramps over any temperature region.

Best regards,


Bob Masta
dqatechATdaqartaDOTcom

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